Searching on "ou"

I have written a program which searches our LDAP database for name
and address info. I am in one division of a large company.
Originally, I set the program with a baseDN of:

o=BigCompanyName,ou=DivisionName,c=US

Then, I got the idea of doing company-wide searches by just deleting
the "ou" term out of the base. So far so good. Then... I got the idea
of letting the user search for someone at a specific division. Since
the division name does not appear to be in any of the other database
fields, I added a search term for "ou=DivisionName"... doesn't work.
I know I am missing something simple... can anyone help?